Hurdles and setbacks

Unfortunately, the company that we ordered the wax filament from had to cancel our order as they no longer had any of this filament and were not able to order in any more of it so we would have to look elsewhere if we wanted it. We spoke with Jouke (our course coordinator) to see if there had been any better results with ordering the cast-able resin but this too was experiencing delays and it did not look like we would get it in time.

We had a phone conference with Maaike on Thursday, 5th of October and let her know that we would not be able to get the samples for Monday and as a result we decided to ask if we could postpone the tests from the casting company. We then discussed with Maaike changing our initial plan of testing to work more with what we currently had available so that we would not have to wait on sourcing and shipping of other materials.

From here it was decided that we would print sample sections of the crown on the Form2 in the standard resin and then test the results of making a silicone mould to produce wax parts for investment casting.

Things are moving quickly

We received an e-mail from Maaike on Monday to ask if we would be able to get samples ready for casting at Groningen by the following Monday. The company she was in contact with had some free time that they could see us and go through the process but there didn’t seem to be too much point travelling there if we didn’t have samples ready for testing. This would mean that we would need to get the cast-able resin and source a printable wax filament by at least Thursday to then have time to print the samples and clean them up ready for Monday the 9th of October. We would also need to crop the scanned crown data to create smaller sample pieces, digitally restore one of these prior to printing and manually restore a sample after printing to be able to compare all of the results.

Our deadlines all changed from our initial meeting but this is something we need to be ready to deal with when it comes to working with industry partners and clients, we would do what we could to get ready in time.

We contacted the Applied Labs and asked when we could book in a time to get an induction for using the Form2 printer and ask about using the wax based filament on their Ultimaker printers. Tessa is the manager of the printing lab area and was very helpful with letting us know where to find all of the tutorial information for using the Form2 printers and running through the introduction for us using the printers ourselves. She also let us know that it was fine to use a different filament on the Ultimaker printers, but that we would have to find out the correct settings for this ourselves. This is what the Form2 printer looks like:

Form2

The wax based filament that we found is called “Moldlay” and it was recommended for use in investment casting. We found a company in the Netherlands that listed this filament on their website and could ship the filament on the same day of order. We placed an order for the filament and continued working on getting everything else ready for Monday. We worked through the tutorials for using the Form2 printer and prepared the digital models for printing samples.

 

Sculpting the 3d models

After scanning the crown on Friday, we took a good look at the result.

Unfortunately, the original crown is quite old and some of the details have been worn off. The following image shows how the loss of details on the ornaments of the crown is clearly visible. Luckily, some sides have more detail than other sides and therefore we know what shape the details have and what we could do to improve them.

The visible loss of detail in the ring of the scanned crown

In addition to the loss of details, the existing paint layer is quite thick and due to the accuracy of the scanner, the lines where the paint was worn off are clearly visible. If the model is printed and cast without smoothening this, the lines will be visible on the cast iron, giving the final product an unwanted finish.

The cracks and paint lines are clearly visible on the model

On top of this, the original structure to mount the crown on the fence is still partially present. Three ‘feet’ were used to stick the crown to the concrete poles. After scanning, the three feet and a bit of concrete is still present in the model. These will have to be removed, since the new way to mount the crown is going to involve a different method.

In order to mount the crown, three feet were added and are still in the scan.

In order to get rid of the paint lines, mounting structure and bring back some of the details, we have a few options during the project. One of the options is to edit the 3D model. Another option would be to retouch the print of the model and depending on the method of casting, the wax can be retouched as well.

We decided to test how hard it would be to digitally retouch the model as this was the most accessible option to begin with. The only problem with this is that most 3d programs do not like the complexity of the model or cannot edit the ‘mesh’ this model consists of. Therefore, we had to search for a program that is able to sculpt 3d models to digitally edit the crown. The following is a list of the programs we used and why they did or did not work for us:

Slicer (Open source: https://www.slicer.org/)

After investigating in a project a few years ago, we read that this project used a CT scan to scan their objects. Using the images, they were able to create a model using Slicer. We hoped that this program also included some modelling options for pre-scanned items, but we were unable to find them.

Meshlab (Open source: http://www.meshlab.net/)

Meshlab is an interesting program for 3d models, since it includes a lot of different filters and options to edit, smoothen and finalise the model. Unfortunately, due to the unfriendly user-interface and the inability to undo actions, simple tasks, such as removing a bump were really difficult.

Geomagic (Wrap) (Trial version: http://www.geomagic.com/en/products/wrap/overview)

Geomagic is a professional program to create scans, edit them and improve models in general. Because this is a professional program, we could only use the trial version. After installing using the “Mesh Doctor”, the limitations appeared. All options were greyed out and you could not save the result.

SculptGL (Open Source: https://stephaneginier.com/sculptgl/)

This web based program was perfect for us. It allowed us to load the object and sculpt it like it is clay by adding, removing and smoothing material. Using this program, we were able to remove the mounts and make the paint layer smoother.

The image below compares the raw scanned crown with the retouch version from SculptGL. Left is before editing and right is after editing. The result is not perfect yet, but the more we can change in the model, the less we have to change once we have a printed version. Bringing back small details is really difficult in the model, so most of the refining has to be done at a later stage.

The comparison between the unaltered model (left) and the edited model (right)

First look at the crown and scanning the model

Today we could finally see the crown in real life! The crown is 14 by 14 by 13 cm large, and quite heavy! It was pretty damaged, just as we expected. A lot of the paint was chipped of and you could see some cracks on the surface. 

Click on the image to get a 360 degrees view!

Top view of the crown

 

Apparently there was a gold layer beneath the paint, which you can still see at some parts. Sadly we do not have enough budget to have gold layers on our reconstructed crowns, so they will be painted.

Bits of the gold paint showing through

When we looked at the crown from up close, we saw that there were a lot of split lines running horizontally from the yellow parts of the crown.

Spit line where two different parts meet

After a quick inspection, it was clear that the crown was casted from six (!) different pieces. We expected it to be one solid piece, so we were surprised about it.

Layout of the different parts

We are going to try to cast it out of one piece, because we would need to make 48 wax or resin moulds otherwise.

One of the problems of the original crowns that they got stolen easily. The crowns had three legs which fit into three holes in the poles. The were glued together with cement. This was not strong enough. We wanted to try a different approach by screwing the crown onto the pole. We will use the knob at the top to attach the screw thread on. We drill a hole with screw thread through the whole length of the crown as well. To prevent someone from unscrewing the knob we will pour glue through the hole of the crown before screwing the knob on.

Possible approach to attach the crown onto the pole

After we discussed some things about the crown we started with the scan. We scanned it in two parts with the Spider.  In the picture you can see the setup.

Set-up

Below is a picture of the raw data and the model. We were very happy with the results. The quality of the scan is really good, you can see the little details like the cracks quite clearly and the paint did not turn out to be a problem.

Raw data of the top part

3D model of the top part of the crown

The underside was scanned as well and the final model can be seen here:

Final 3D model with top and bottom part combined

We did it all in one go so the whole process went extremely smoothly. The 3D model can be saved as an stl file, so we will try to retouch the crown as best as we can. We will try to retouch it with Rhino, if that does not work we will try out other programs.

Playing around with the 3D scanner

Before we can scan the crown and make a 3D model we need to practise with the scanners. Maaike arranged for us a meeting with Bertus Naagen, a staff member at the TU Delft who has a lot of experience with 3D scanning. He introduced us to the two scanners they used at the faculty: the Artec Spider and the Artec Eva. We learned that the Artec Spider is used for larger objects which can be scanned from a larger distance. The Artec Eva is better used for smaller objects to scan in a closer range because it can scan more details.

Artec spider

Artec Eva

With help from Bertus we started with a scan of a statue of a penguin to try out the program and the machine. Both Artecs can be operated by hand but you can also put them on a tripod to reduce shaking. Because we wanted to scan every side of the penguin we used a rotating platform with a stool on top where the penguin could stand on.

Set up with the tripod and rotating platform

It took some practice to get used to the scanning, but at the end of the morning we learned a lot and were able to do a scan on our own. We learned that you have to move the tripod with the machine on it slowly. You have to be careful that all the parts are scanned, but the scan should not be too long otherwise the file is too large to process. If the shape is too complex to scan in one go, you can make two scans and merge them together with the software. We did this with the penguin as well, one scan from the top and one from the bottom and afterwards we aligned the two. We will need to do this for our crown as well if we want all the details to be there on the 3D model. After we made our first scan Bertus showed us how to make a model out of the raw data. We also learned some tricks such as erasing the ground from the scan and putting texture on the model. Once you know the basics, the program is quite easy to use.

After the basic instruction we could play around so we made some more scans, for example this one:

Example of a test 3D scan

3D model of Vivians face

Rohan and his 3D model

We also scanned our own faces which was really awesome. We first tried it with the Artec Spider but that didn’t really work so we switched to the Eva scanner.

Hair has a very fine texture and shines a lot so that is why the scanner could not scan our hair properly. Form Bertus we heard that he had some trouble with scanning shiny objects in the past. Sometimes he sprayed dry shampoo on the objects to make it more matte. We wonder if the crown will be too shiny for the scanner because of the paint. Hopefully it will work out.

First day of the project

Today we met Maaike de Vries, our coach for this project. She gave us an introduction on what we are going to do during these four weeks. She told us that we will work together with Paleis het Loo to reconstruct royal monument the Naald in Apeldoorn. It was built in 1901 as a gift for the marriage of queen Wilhelmina and Prince Hendrik. In 2009 the monument was mentioned a lot in the news because an attack on the royal family was attempted there during the national Kings day. The monument is obelisk shaped and has a round gate with eight poles surrounding it. Below you can see some original pictures of the monument from the opening in 1901.

Opening in 1901

Detail of the gate

This is what the monument looks like now.

Monument in 2009

If you look closely you can see that the crowns from the original picture are missing. Around 1950 so many of the crowns were stolen or damaged that Paleis het Loo decided to remove the remaining crowns and include them in their collection. This year Het Loo wanted to give the monument back its crowns by making eight brand new pieces which are reconstructed from the original crowns and they asked us and Maaike to do so! We are all very excited to start working on this project.

The original crowns were made of cast iron. We are going to cast the reconstructed crowns as well by a company in Groningen called gieterij Borcherts. They do investment casting, a process where you have a replica of the object that you want to cast made out of material that will melt. The mold is created by putting sand around the replica and then heating it up so that the replica melts away. Iron is poured into the created cavity. When the object is cooled down the sand will be brushed away.

 

Explanation of investment casting

Because casting eight crowns will take a lot of time, we will not be able to finish them before the project deadline. However, we can still cast some test pieces to try out which casting method works best. For now we want to try out three moulds:

  1. A wax mould made by pouring wax in a silicon mould. The silicon mould is created with a 3D printed crown made out of PLA

      2. A 3D printed wax mould made out of wax filament which will be printed in the Ultimaker 3

      3. A castable resin mould which is printed on a Form2 machine

To make the moulds we will make a 3D model of the crown and retouch it digitally.

We heard a lot of information today and we are excited to start working on the project. For now we will figure out how to make a 3D model of the original crown so stay tuned for another blog post!

 

Introduction

Hello and welcome to our blog! We are Tom Salden, Vivian Vriend and Rohan McEvoy and we do the minor Advanced Prototyping at the TU Delft. In this minor we get the opportunity to work on a four week long project about advanced production techniques. Our project is called: Reconstructing a royal monument. In our project we will explore the possibilities of 3D scanning, modelling and printing combined with traditional, historical cast-iron techniques to restore a monument in the Netherlands. In this blog we will keep you updated on our progress, and hopefully make you more enthusiastic.